Electrical calculator
Know any two of voltage, current, resistance and power? The other two follow from Ohm's law — pick which pair you have and this calculates the rest.
Energy calculator
A device's power rating and how long it runs determine the energy it uses — the number your electricity bill counts in kWh.
Why you can't convert volts to joules
Volts and joules measure different things, so there is no fixed "1 V = X J" factor. Voltage (volts) is electrical pressure, current (amps) is how much charge flows, power (watts) is how fast energy is delivered, and energy (joules) is the total amount delivered. They connect only through the real formulas: power = voltage × current (P = V × I), and energy = power × time (E = P × t). A 230 V outlet by itself tells you nothing about energy until something draws current through it for some amount of time.
Which formulas does this calculator use?
Ohm's law (V = I × R) and the electrical power law (P = V × I), plus the combinations that follow from them: P = V²/R, P = I² × R, V = √(P × R), and so on. The energy calculator uses E = P × t, with 1 Wh = 3600 J and 1 kWh = 3.6 million J.
Does this work for AC (wall power) too?
Yes for simple resistive loads (heaters, kettles, incandescent bulbs), where these formulas apply directly using RMS values — which is what "230 V" already is. For motors and electronics, real AC power also involves a power factor, so treat the result as the upper bound (apparent power).
Is my data sent anywhere?
No — this runs entirely in your browser with plain JavaScript. Nothing is uploaded.